Valorization of by-products from the agro-industrial sector in Côte d’Ivoire: Lactic Acid production from cashew apple juice supplemented with sugarcane molasses

Côte d’Ivoire, the global leader in cashew nut production, largely abandons cashew apples after harvest. Similarly, sugarcane molasses, a by-product of sugar production, is underutilized. This study proposes an innovative method to valorize these two agricultural residues by producing lactic acid using the bacterium Lactobacillus casei NRRLB-441. The approach combines cashew apple juice and sugarcane molasses to create an optimized culture medium, offering promising economic and ecological opportunities. To achieve this, an I-optimal mixture design was implemented, with cashew apple juice proportions ranging from 50% to 90%, and sugarcane molasses from 10% to 50%. An experimental matrix of 13 trials, based on the Scheffé model, was developed to determine optimal combinations and measure lactic acid yields. This approach aims to maximize the utilization of these agricultural residues while providing promising economic and environmental prospects. Biochemical and mineralogical analyses revealed that cashew apple juice and sugarcane molasses are rich in glucose (82.78 g/L), fructose (66.65 g/L), and minerals (calcium, magnesium, iron, sodium, and potassium). The results showed a significant lactic acid concentration (78.57 g/L) when cashew apple juice and sugarcane molasses are in equal proportions (50%), with a yield of 69.22% and a productivity of 1.09 g/L/h. These findings confirm the bio-convertibility of these agro-resources into other economically significant products such as lactic acid, citric acid, and bioethanol.